linux-kernel - [PATCH 1/1] docs: static initialization of spinlocks is OK

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Message-ID: <20070703163356.GF30089@coraid.com>
Date:	Tue, 3 Jul 2007 12:33:56 -0400
From:	"Ed L. Cashin" <ecashin@...aid.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Greg K-H <greg@...ah.com>
Subject: [PATCH 1/1] docs: static initialization of spinlocks is OK

Static initialization of spinlocks is preferable to dynamic
initialization when it is practical.  This patch updates documentation
for consistency with comments in spinlock_types.h.

Signed-off-by: Ed L. Cashin <ecashin@...aid.com>
---
 Documentation/spinlocks.txt |   20 +++++++++++---------
 1 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/Documentation/spinlocks.txt b/Documentation/spinlocks.txt
index a661d68..471e753 100644
--- a/Documentation/spinlocks.txt
+++ b/Documentation/spinlocks.txt
@@ -1,7 +1,12 @@
-UPDATE March 21 2005 Amit Gud <gud@....net>
+SPIN_LOCK_UNLOCKED and RW_LOCK_UNLOCKED defeat lockdep state tracking and
+are hence deprecated.
 
-Macros SPIN_LOCK_UNLOCKED and RW_LOCK_UNLOCKED are deprecated and will be
-removed soon. So for any new code dynamic initialization should be used:
+Please use DEFINE_SPINLOCK()/DEFINE_RWLOCK() or
+__SPIN_LOCK_UNLOCKED()/__RW_LOCK_UNLOCKED() as appropriate for static
+initialization.
+
+Dynamic initialization, when necessary, may be performed as
+demonstrated below.
 
    spinlock_t xxx_lock;
    rwlock_t xxx_rw_lock;
@@ -15,12 +20,9 @@ removed soon. So for any new code dynamic initialization should be used:
 
    module_init(xxx_init);
 
-Reasons for deprecation
-  - it hurts automatic lock validators
-  - it becomes intrusive for the realtime preemption patches
-
-Following discussion is still valid, however, with the dynamic initialization
-of spinlocks instead of static.
+The following discussion is still valid, however, with the dynamic
+initialization of spinlocks or with DEFINE_SPINLOCK, etc., used
+instead of SPIN_LOCK_UNLOCKED.
 
 -----------------------
 
-- 
1.5.2.1
-
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